1. Field of the Invention
The present invention relates to a wireless communication antenna system, and more particularly, to a built-in antenna system for indoor wireless communications.
2. Description of the Related Art
The use of wireless communication appliances having high mobility, such as a web pad, has become quite popular due to advances in home networks. Accordingly, much attention has been directed to improve the performance of a built-in antenna in order to increase the quality of wireless communications.
Generally, indoor wireless communications are performed mainly between an access point (AP) of a wireless local area network (LAN), which has low or no mobility, and a notebook computer. For this reason, low attention has been paid to indoor wireless communications.
The quality of indoor wireless communications is closely related to the indoor wireless environments. Therefore, the indoor wireless environments need to be first considered before addressing factors to increase the quality of indoor wireless communications.
The indoor wireless environments may depend on the type of architectural or residence style, that is, they may vary from country to country or region to region. For instance, the physical structure of houses constructed with non-metallic materials, such as sheet rock or plaster boards, do not block electric (or radio) waves. Accordingly, indoor wireless communications are not likely to be affected by the shape or location of an antenna.
In contrast, apartments, made with steel reinforcements or steel frame structures, block the propagation of electric (or radio) waves. Therefore, the quality of wireless communications depends on the shape or location of an antenna.
Referring to FIG. 1, in a conventional indoor wireless communication system, an AP 12 and an antenna 12a for the AP 12 are combined together and installed on one surface of a wall 10. Thus, a signal transmitted from the antenna 12a is propagated only in one direction due to the wall 10. In this case, the signal is successfully transmitted to a first wireless communication terminal 14 which is installed on a line of sight of the antenna 12a. However, the signal may be weakened or may not be transmitted to the second terminal 16 during the transmission of the signal to a second wireless communication terminal 16 located behind the wall 10. Also, the presence of the wall 10 causes a shift in a frequency band of the antenna 12a. 
In general, the antenna 12a is installed in a living room and a beam pattern transmitted from the antenna 12a has a single directionality, when the system of FIG. 1 is used in an apartment unit. Thus, it is possible to stably conduct wireless communications in the living room but the speed of communication may be reduced or communications may be impossible in other rooms of the apartment unit.
The installment of several APs in an apartment unit reduces the occurrence of the aforementioned problem in a wireless communication adopting a wireless communication appliance of low mobility. However, interferences of electric (or radio) waves is still a serious problem in a wireless communication adopting a wireless communication appliance of high mobility.
As mentioned above, a conventional antenna system for indoor wireless communications is capable of supporting high-quality wireless communications for a wireless communication terminal that is installed on a line of sight of an antenna for an AP. However, with the conventional antenna system, it is difficult to support high quality wireless communications for a wireless communication terminal that deviates from the line of sight of an AP antenna, for example, when there is a wall between the terminal and the AP antenna. In a worst case scenario, wireless communications cannot be conducted with the wireless communication terminal using the conventional antenna system. In particular, a frequency band of the antenna for an AP is more likely to shift when the AP antenna is installed adjacent to a wall.